1. Field of the Invention
This invention relates to a power conversion apparatus which controls an AC motor for driving, for example, a vehicle, and more particularly to the mechanical configuration thereof.
2. Description of the Related Art
In general, a power conversion apparatus for controlling the driving motor of a vehicle in a hybrid automobile, an electric automobile or the like includes as its principal constituents, power modules each of which includes power semiconductor elements for converting powers between DC and AC, a control circuit board on which components constituting a control circuit for controlling the power semiconductor elements of the power modules are packaged, a smoothing capacitor, and bus bars which electrically connect the power modules and the motor. The constituents are arranged and fixed in correspondence with the mounting structure of the vehicle.
In such a power conversion apparatus, there has been a prior-art apparatus wherein, in view of increase in the number of the power modules (IPMs) to-be-installed in which the power semiconductor elements for converting the powers are included, the IPMs are vertically erected and are arranged and fixed so that they can be arranged without enlarging a floor area. (Refer to, for example, JP-A-2004-215340 which shall be called “Patent Document 1” below.)
Further, there has been a prior-art apparatus wherein the resin-molded plate portion of a plate having built-in bus bars is provided with a central support post, and the central support post is held in abutment on the tentative surface of a printed circuit board on which the control circuit is packaged, so as to suppress the vibrations of the printed circuit board. (Refer to, for example, JP-A-2003-324903 which shall be called “Patent Document 2” below.)
In addition, there has been a prior-art apparatus wherein pins for the control signals of the switching semiconductor element modules are formed with crooked portions each of which is endowed with a flexibility by a bending work, so as to absorb displacements developing due to vibrations or the difference of thermal expansions, by the crooked portions. (Refer to, for example, JP-A-2005-85958 which shall be called “Patent Document 3” below.)
Regarding an equipment which is installed on a vehicle, however, a space allowed for the installation is severely restricted. A versatility for the installation on the vehicle is not always high, merely by the contrivance in which the elements constituting the equipment are arranged substantially vertically as in the prior-art apparatus stated in Patent Document 1. Further, in the prior-art apparatus, the control circuit board for controlling the drives of the power modules (IPM drive circuit board) is fixed on a base side through a cover member, and any configurational consideration for enhancing vibration-proofness is not made.
Besides, according to the prior-art apparatus stated in Patent Document 2, the printed circuit board is not supported at any part other than its peripheral edge part and the part abutting on the central support post. Accordingly, a resonance point ascribable to the vibrations is inevitably existent, and displacements caused by the resonance of the printed circuit board attributed to the resonance frequency of the resonance point develop, so that electric components and electronic components packaged on the printed circuit board, or structural components are apprehended to damage or fall off. Further, the prior-art apparatus has not a structure which emits heats generated by the electronic components, etc. packaged on the control circuit board, and it is problematic in durability and reliability.
Besides, in the prior-art apparatus stated in Patent Document 3, the pins for the control signals as are disposed in the power modules including the switching semiconductor elements include the crooked portions each of which has been subjected to the bending work so as to ensure the flexibility. In general, however, it is difficult to perform a work of high precision by the bending work. In an assembling structure which requires a comparatively minute dimensional precision as in case of inserting the control signal pins of the power modules into holes provided in a printed circuit board, as in the power conversion apparatus which is installed on the vehicle, there is the problem that all the pins cannot be inserted due to dimensional deviations in some cases.